Preparation of diamine carbamates

ABSTRACT

Diamine carbamates are prepared by spraying liquid diamine into carbon dioxide gas, in the optional presence of a propellant.

This Appln claims the benefit of U.S. Provisional No. 60/011,246 filedFeb. 6,1996.

FIELD OF THE INVENTION

This invention relates to an improved process for the preparation ofdiamine carbamates by contacting a liquid diamine with carbon dioxidegas.

TECHNICAL BACKGROUND

Polyamine carbamates have been produced in the past by adsorbing thepolyamine on a particulate carrier and then reacting the polyamine withcarbon dioxide. See Brodoway U.S. Pat. No. 4,102,801.

Another route to carbamate salts is to react an amine in solution withgaseous or dissolved carbon dioxide.

Hexamethylene diamine carbamate has been prepared by the known processof reacting hexamethylene diamine and carbon dioxide in chlorobenzenesolvent.

Leon Segal in Applied Spectroscopy Vol. 17, No. 1, 1963 at pages 21-22,discloses the reaction of hexamethylene diamine in the solid state withatmospheric carbon dioxide.

Polyamine carbamates are useful as curing agents for elastomers. Theprimary diamine carbonates prepared by the process described herein areuseful as intermediates for the preparation of polyamides.

SUMMARY OF THE INVENTION

This invention provides a process for the preparation of primary diaminecarbamates which comprises reacting a liquid spray of primary diaminewith gaseous carbon dioxide, in the optional presence of an inertpropellant.

DETAILED DESCRIPTION OF THE INVENTION

The process of the present invention concerns the preparation of primarydiamine carbamates by the spraying of a liquid primary diamine intocarbon dioxide gas, optionally in the presence of an inert propellant.The diamine must be utilized above its melting point, i.e., in theliquid state. If the melting point of the diamine starting material liesabove room temperature, or above whatever other temperature is chosen tobe the temperature of the reaction, the diamine must first be heatedabove its melting temperature to allow for spraying.

The liquid diamine is propelled by pressure into the gaseous carbondioxide, optionally using an inert gas, for example, but not limited to,nitrogen as a propellant.

Suitable diamines include primary aliphatic, cycloaliphatic, andaromatic diamines having 2-14 carbon atoms. The most preferred diamineis hexamethylene diamine. The melting point of industrially prepared,commercially available hexamethylene diamine is 39-40° C., and thus, thehexamethylene diamine must be heated above this temperature prior toreaction.

The process of the present invention avoids the problems of solventhandling prior to and during reaction and the effort associated withsolvent removal from the diamine carbamate product that is required bysome available processes and avoids the need for cryogenic grinding asrequired in other processes.

The process of the invention for primary aliphatic diamines may besummarized by the following equation for linear aliphatic primarydiamines where x is a number from 2-14:

    H.sub.2 N(CH.sub.2).sub.x NH.sub.2 (liquid)+CO.sub.2 (gas)→+H.sub.3 N(CH.sub.2).sub.x NHCOO--(solid)

Spraying the molten amine into the carbon dioxide causes it to reactvigorously, promptly, and completely. The diamine, the carbon dioxide orboth may be mixed with an inert gas propellant to insure prompt andintimate contact between the diamine and the carbon dioxide. Thespraying of the molten diamine in small droplets insures maximum contactsurface and for the rapid reaction of diamine with the carbon dioxide.

In general, the smaller the droplet size, the easier it is to completereaction. For each diamine employed, the optimum droplet size will vary.Optimum particle size for each diamine may be readily determined. Underoptimum droplet size conditions, the reaction will be complete in ashort time, essentially instantaneously.

It is, of course, necessary for the carbon dioxide to be present in thereaction zone in an amount at least stoichiometrically equal to theamount of diamine in order to achieve complete reaction. Usually carbondioxide is present in the reaction mass in excess of the stoichiometricamount.

Carbon dioxide may be used at room temperature and may be used with aninert propellant such as nitrogen gas.

Representative amines that may be employed in the process of thisinvention include: 1,3-diaminopropane, 1,6-diaminohexane (hexamethylenediamine), 1,2-diaminoethane, 1,4-diaminobutane, 1,5-diaminopentane,1,10-diaminodecane, 1,12-diaminododecane, 1,4-diaminocyclohexane,4,4'-methylenebis(cyclohexylamine), 1,4-phenylenediamine, and1,3-phenylenediamine. Preferred diamines are 1,6-diaminohexane(hexamethylene diamine), 1,12-diaminododecane and4,4'-methylenebis(cyclohexylamine). Most preferred is 1,6-diaminohexane(hexamethylene diamine).

In the following example all parts and percentages are in parts byweight unless otherwise specified.

EXAMPLE 1 Preparation of Hexamethylene Diamine Carbamate

Hexamethylene diamine, 98.5% pure, 35 g, was charged to a 125 mLnitrogen pressurized atomizer. The hexamethylene diamine in the atomizerwas heated by means of a hot water bath on a stirrer/hot plate toapproximately 35° C. The outlet of the atomizer was directed toward theopening of a rectangular receiver constructed of corrugated paper boardcoated with a Teflon® fluoropolymer film. A stream of carbon dioxide gasfrom a laboratory sized cylinder was directed through a dispersingfunnel at the rear of the hexamethylene diamine charged atomizer so asto encompass the hexamethylene diamine spray in a concurrent flow ofcarbon dioxide. The atomizer spray tip was indirectly heated with aninfrared heat lamp to avoid a build up of hexamethylene diaminecarbamate product. The carbon dioxide flow was started followed bystartup of the hexamethylene diamine spray. The finely dividedhexamethylene diamine droplets were instantly converted to a fine whitepowder that melting point determination (m.p. 150-160° C.) proved to bepredominantly hexamethylene diamine carbamate.

What is claimed is:
 1. A process for the preparation of primary diaminecarbamates which comprises reacting a liquid spray of primary diaminewith gaseous carbon dioxide, in the optional presence of an inertpropellant.
 2. The process of claim 1 in which the diamine is selectedfrom the group consisting of aliphatic and cycloaliphatic diamineshaving 2-14 carbon atoms.
 3. The process of claim 1 wherein the amine isselected from the group consisting of 1,2-diaminopropane,1,6-diaminohexane (hexamethylene diamine), 1,2-diaminoethane,1,4-diaminobutane, 1,5-diaminopentane, 1,10-diaminodecane,1,12-diaminododecane, 1,4-diaminocyclohexane,4,4'-methylenebis(cyclohexylamine), 1,4-phenylenediamine, and1,3-phenylenediamine.
 4. The process of claim 3 in which the amine is1,6-diaminohexane (hexamethylene diamine).
 5. The process of claim 3 inwhich the amine is 1,12-diaminododecane.
 6. The process of claim 3 inwhich the amine is 4,4'-methylenebis(cyclohexylamine).
 7. The process inclaim 1 conducted in the presence of an inert propellant.
 8. The processof claim 7 wherein the propellant is nitrogen gas.